Our long-range goal is to increase knowledge of the neonatal development of the gas-exchange region of the lung. Our more immediate goal is to learn more about a lectin that is found in the lung of several species including rat and man. In rat lung, lectin activity peaks at the same time the lung is undergoing its period of intense postnatal alveolarization. We think the key issues and the importance of our work relates to the possibility that the lectin may play a critical role in lung alveolarization. Our aim in this proposal is to solidify (or exclude) the association of lectin and alveolarization. We plan to do this by 1) testing the association of lectin activity and alveolarization in two additional species (guinea pig for pre-natal and mouse for post-natal alveolarization), and 2) by experimentally altering the time of alveolarization in the rat. We further propose to study the temporal anatomical appearance of the lectin during the stage of alveolarization. Finally, we plan to study the mechanism by which the lectin rises during the period of alveolarization and examine factors that might modulate the change in lectin activity. We hope to achieve our goals using techniques of cell physiology and cell biology to understand this aspect of lung development. We think our studies will provide important information on the molecular and cellular basis of lung development and may provide a basis for understanding developmental defects of the lung.